With the recent increase in the baseball-playing population, a so-called screen baseball system has emerged that overcomes the limitations of playing baseball in a wide baseball field and allows people to enjoy a virtual baseball game in a small indoor space through virtual reality.
Typically, a screen baseball system is installed in an indoor space and has a batter's box with a space of a predetermined size where a user can bat and a screen capable of displaying a virtual baseball field. When a pitching machine installed behind the screen pitches a ball toward the batter's box, a user preparing to hit the ball in the batter's box hits the ball pitched by the pitching machine. At this time, a sensing apparatus senses movement of the pitched ball and the movement of the ball hit by the user. Then, based on the result of sensing, it is determined whether the pitch is a ball or strike, and a simulation image of the trajectory of the hit ball is implemented on the screen.
In such a screen baseball system, a hole is formed in the screen onto which a baseball simulation image is projected, and a pitching machine installed on the back of the screen pitches a ball through the hole formed in the screen.
The technology related to screen baseball systems using a pitching machine as described above is disclosed in many prior art documents including Korean Patent Application No. 10-2001-7011084, Korean Patent Application No. 10-2014-0058124, Korean Patent Application No. 10-2009-0063347, Korean Patent Application No. 10-2010-0079368, Korean Patent Application No. 1990-7002659, Japanese Unexamined Patent Application Publication No. 09-276467, and Korean Patent Application No. 1994-0023057.
However, for a majority of conventional technologies related to the screen baseball systems including the aforementioned prior art documents, a hole large enough to allow a baseball to pass therethrough is formed in the screen and a pitching machine located behind the screen fires a ball toward the batter's box through the hole formed in the screen. In this case, when an image is projected onto the screen, the image is not displayed at the position of the hole through which the ball passes. Instead, a part of the pitching machine is seen through the hole. As a result, immersion in the image projected onto the screen is seriously deteriorated from the perspective of the user and interest in the screen baseball game is greatly lowered.